A variety of engineered flow management structures are commonly used to store, manage, distribute, produce, sample and prospect for water. Man-made dams of earthen or other engineered materials are commonly used as barriers to flow and/or to store and manage surface water resources. Man-made levees and canals of earthen or other engineered materials are commonly used to divert, contain and distribute surface water. Slurry walls, grout curtains, and retaining walls are constructed to restrict, divert, or direct the flow of subsurface groundwater. Wells and boreholes which contain engineered structures are commonly used to prospect for, produce, and manage groundwater resources.
Wells are also constructed to achieve other flow management purposes. For example a well can be cased with cement, PVC pipe, or any number of other engineered materials to allow for controlled extraction of subsurface fluids or gas. Cased wells are often screened or perforated within in certain intervals, to facilitate flow of water, hydrocarbons or other fluids from a subsurface formation to the inner casing of the well. Within intervals where wells are cased and not screened or perforated, it is commonly desirable that well casings provide a barrier to fluid flow into or out of the well.
Sometimes an annular space between the casing or screen and the surrounding formation is backfilled with earthen or other engineered materials such as gravel, sand, cement or grout to affect fluid movement. For example, impermeable materials such as bentonite, grout and cement are often introduced in this annular space to act as a barrier to flow within the annular space. On the other hand, more permeable materials such as gravel and sand are often introduced into the annular space to facilitate the free flow of groundwater between the formation and the well. Such engineered well completions including filter packs and/or grouting are important for controlling and maintaining flow within a well and the structural stability of the well, whether for the purpose of extracting groundwater, other fluids, or gases from the formation or for the purpose of injecting fluids into the formation.